This invention pertains to uniquely keying two parts together amongst a plurality of such parts.
U.S Pat. No. 3,818,280 discloses a keying structure that is a part of a printed circuit board connector.
The lower edge of the circuit board has permanently cutout slots along the lower edge. A separate strip of circuit board material is removably locked within the connector so that such a strip can be chosen that corresponds with upstanding tabs that enter the slots in the circuit board.
The code of the circuit board cannot be changed, but the entry into another connector can be accomplished by moving the separate strip that corresponds to the slots in the circuit board to that other connector.
U.S. Pat. No. 3,447,036 discloses a keying assembly for mounting and aligning rectangular modules. Four square holes are provided into which a relatively thin rectangular male piece is oriented to one of four possible positions.
Female coding plugs are preadjusted to mate with only one of the sets of male coding plugs.
A maximum of 256 codes are available.
Other structural constraints are used to align the modules.